Rebuilding a Set of Type AA Crossovers.

Here I will show the basic steps for rebuilding a set of Type AA crossovers.

I think the last of these were built in around the early 1980s.  I think generally we can consider any crossover that is at least 20 years old needs at least the capacitors replaced.  Normally all the other parts on the crossover are good.  

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Here is what we send you as a kit to use to rebuild the type AA crossovers.

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Ready to start the rebuild.   You don't need all the tools we have here.  Minimum would be a soldering iron, solder, a phillips tip screwdriver and wire cutters.

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Now around here, we normally just remove all the parts from the board and then clean up the board before putting everything back together.  For this demonstration, we will just do the rebuild in small steps.  In case you haven't done hundreds of these rebuilds like we have, you may want to just follow these steps.  Also, we are using a few things you may not have in our rebuilds.  The red sleeving you will see on the capacitor leads and the black shrink sleeving we use to cover the solder joints are something we use mostly for looks.  Your rebuild will work just as well without those "neatness" items.

We will start with the old 13 uF capacitor.  Just snip the leads off.

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Remove the two screws holding the old 13 uF cap in place.  

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Since one of the screws was also holding down one side of the autotransformer, put that screw back in the tab for the autotransformer after removing the cap.

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Use the other screw you removed from the old cap mounting to install the new plastic cap mounting block.

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Install the new 13 uF cap on the cap mounting block using a tie wrap.

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Strip some insulation from the wires you removed earlier from the old 13 uF cap and connect one of them to each of the new 13 uF cap leads.  Doesn't matter at all which wire goes to which lead.  This is a crossover.  It handles only AC signals.  Therefore there cannot be any polarity for the capacitors.  

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All right, one cap down and two to go.  Now snip off the wires going to the next cap (2 uF) to the left.  Notice that this time there are two wires connected to one side of the cap and only one on the other side.  Make sure you keep the two that went to one side together so that you can connect both of them together to one lead of the new cap.  Again, doesn't matter which side of the new cap they connect to.

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Now let's attack the last cap. 

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Here again, we are dealing with two wires to one side of the cap.  Just keep those two wires together like you did on the last cap we installed.

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OK, we will just tidy things up a bit now and we will be finished.

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This is about the time in this rebuild that I noticed something I have seen before and need to address it.  Look at the little inductor that is in the left back corner of the crossover.  That is a 245 uH air core inductor that is part of the tweeter circuit.  For some reason, at the factory, they sometimes used a regular steel screw in these inductors.  Should be a non-magnetic screw or the inductance will not be the specified 245 uH but instead will be around 350 uH.  This one has the wrong screw in it from the factory.  You can check the screw with a magnet.  If it is attracted to a magnet, it is wrong and should be replaced.

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Here are two of the correct screws and the incorrect one I just removed from the 245 uH inductor.  Notice that the one that was installed at the factory is strongly attracted to the magnet.  The other two are not attracted at all.  The ones I use are stainless steel.  Brass would also be good.  Just test whatever screw you use with a magnet.

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B & K Sound, 1925 East Gum Log Rd. Russellville, AR, 72802 phone-479-967-1542